The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions with high surface loadings. In embodiments, there are provided in accordance with the present invention toner compositions comprised of resin particles, pigment particles, and with surface additives wherein the toner area surface area is from about 30 to about 80 percent. The present invention is also directed to imaging processes, especially xerographic imaging and printing processes with toners containing additives thereon in an amount that enables coverage of from about 30, and preferably 32 to about 80 percent of the surface area of the toner, and which processes permit excellent toner and image transfer efficiency and reduced image deletion defects. More specifically, in embodiments of the present invention the toner selected displays a high transfer efficiency as a function of the gap, or spacing between the photoconductor and the substrate, such as paper, resulting in decreased image or character deletion counts as compared, for example, to prior art toners with less than or equal to about 17 weight percent surface area coverage. Especially preferred in embodiments of the present invention are toners with an average volume diameter of from about 6 to about 10, and preferably about 7 microns. Also, in embodiments the toner compositions of the present invention possess excellent admix characteristics and maintain their triboelectric charging characteristics for an extended number of imaging cycles exceeding, for example, 500,000 in a number of embodiments.
Toner and developer compositions are generally known. Also known are toners with resin, pigment, usually present in an amount of from about 2 to about 8 weight percent, and wherein the pigment can be carbon black, cyan, magenta, yellow, and the like, and which toner may also contain a charge enhancing additive, reference for example U.S. Pat. Nos. 4,338,390 and 4,298,672. There can also be blended with toner compositions external additive particles including flow aid additives, which additives are usually present on the surface thereof, and wherein the additives are added to the toner in amounts of from about 0.1 to about 1 weight percent, or wherein the toner surface coverage by area is believed to be about from 1 to about 15 percent. Examples of these additives include colloidal silicas, such as AEROSIL.RTM., metal salts and metal salts of fatty acids inclusive of zinc stearate, aluminum oxides, cerium oxides, titanates like strontium titanate, and mixtures thereof, which additives are generally present in an amount of from about 0.1 percent by weight to about 5 percent by weight, and preferably in an amount of from about 0.1 percent by weight to about 1 percent by weight. Several of the aforementioned additives are illustrated in U.S. Pat. Nos. 3,590,000 and 3,800,588, the disclosures of which are totally incorporated herein by reference.
Also known are toners of small particle size, for example from about 3 to about 7 microns in average volume diameter, and which toners may minimize paper curl. There is illustrated in U.S. Pat. No. 4,996,127 a toner with an average volume diameter of from 3 to about 7 microns, of associated particles of secondary particles comprising primary particles of a polymer having acidic or basic polar groups, and a coloring agent. The polymers selected for the toners of this '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing the required amount of coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. Also, note column 9, lines 50 to 55, wherein a polar monomer, such as acrylic acid, in the emulsion resin is necessary, and toner preparation is not obtained without the use, for example, of acrylic acid polar group, see Comparative Example I. In U.S. Pat. No. 4,983,488 is illustrated a process for the preparation of toners by the polymerization of a polymerizable monomer dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component, and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation have diameters suitable for a toner. It is indicated in column 9 of this patent that coagulated particles of 1 to 100, and particularly 3 to 70 are obtained. This process is thus directed to the use of coagulants, such as inorganic magnesium sulfate which results in the formation of particles with wide GSD. Also of interest are U.S. Pat. No. 4,797,339, wherein there is disclosed a process for the preparation of toners by resin emulsion polymerization, wherein similar to the '127 patent polar resins of oppositely charges are selected, and U.S. Pat. No. 4,558,108, wherein there is disclosed a process for the preparation of a copolymer of styrene and butadiene by specific suspension polymerization.